We investigated the effect of the excitation wavelength on the density evolution of laser-produced tin plasmas, both experimentally and numerically. For producing plasmas, Sn targets were excited with either 10.6 lm CO 2 laser or 1.06 lm Nd:yttrium aluminum garnet laser; both are considered to be potential excitation lasers for extreme ultraviolet lithography laser-produced plasma light sources. The electron density of the plasma during the isothermal expansion regime was estimated using an interferometric technique. The Stark broadening of isolated singly-ionized emission was employed for deducing the density during the plasma adiabatic expansion regime. Our results indicate that the excitation source wavelength determines the initial density of the plasma, as well the plume expansion dynamics. Numerical simulation using HEIGHTS simulation package agrees well with the experimentally measured density profile. V

Tungsten is the leading high-Z candidate surface material for magnetic fusion reactor plasma-facing components, however, there are specific performance concerns for tungsten, and a general major concern about relying on one material. To broaden the options for fusion development we identified and examined five potential alternative high-Z plasma-facing materials: zirconium, niobium, molybdenum, hafnium and tantalum. We assess these materials from three standpoints: neutroninduced activation, sputter erosion/redeposition and plasma transient response. This initial analysis is encouraging showing (1) environmentally attractive activation properties with minimum waste disposal, for a tokamak reactor divertor, using advanced recycling techniques, (2) acceptable sputtering erosion/redeposition performance, similar to a tungsten divertor, and (3) concerns about the transient response of the alternative materials, but not fundamentally different than concerns for tungsten. We identify work needed to advance the qualification of these materials.

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Extreme ultraviolet (EUV) lithography devices that use laser produced plasma (LPP), discharge produced plasma (DPP), and hybrid devices need to be optimized to achieve sufficient brightness with minimum debris generation to support the throughput requirements of High-Volume Manufacturing (HVM) lithography exposure tools with long lifetime. Source performance, debris mitigation, and reflector system are all critical to efficient EUV collection and component lifetime. Enhanced integrated models are continued to be developed using HEIGHTS computer package to simulate EUV emission at high power and debris generation and transport in multiple and colliding LPP. A new center for materials under extreme environments (CMUXE) is established to benchmark HEIGHTS models for various EUV related issues. The models being developed and enhanced include, for example, new ideas and parameters of multiple laser beams in different geometrical configurations and with different pre-pulses to maximize EUV production. Recent experimental and theoretical work show large influence of the hydrodynamic processes on EUV generation. The effect of plasma hydrodynamics evolution on the EUV radiation generation was analyzed for planar and spherical geometry of a tin target in LPP devices. The higher efficiency of planar target in comparison to the spherical geometry was explained with better hydrodynamic containment of the heated plasma. This is not the case if the plasma is slightly overheated. Recent experimental results of the conversion efficiency (CE) of LPP are in good agreement with HEIGHTS simulation.